Kiwi Ears Halcyon

A New Kind of Tribrid, Built Around Kiwi Ears’ First MEMS Driver

Refined, beautifully built, and — more than anything else — one of the most comfortable IEMs I have worn.

Kiwi Ears describes the Halcyon as one of the first in-ear monitors to build a tribrid around a solid-state MEMS driver. The more useful point for a buyer is that this driver combination is unusual at $259: a 10mm composite-diaphragm dynamic driver handles the bass, two customised Knowles DEK-series balanced armatures cover the midrange, a customised Knowles WBFK armature takes the treble, and the MEMS driver sits above that on the upper highs alone. The MEMS driver is the part Kiwi Ears puts in the spotlight, and it gets its own section below — though the dynamic driver and the two DEK armatures are doing real work of their own on bass and midrange, as the sound section covers.

It launched as a Kickstarter project, where backers paid $199; with that promotion now finished it retails for $259. Kiwi Ears describe the tuning as their house studio-monitor signature: a sub-bass shelf cut at 200Hz, neutral mids, and a 3kHz peak for pinna-gain compensation. My own measurements are further down, and they line up with that description closely.

This is the best of the three Kiwi Ears products I have been using, and the one I was most curious about — a genuine tribrid with a driver type that is still rare in shipping products leading the treble. MEMS has existed for years in other applications; what is new is seeing it used as a driver in a finished IEM rather than a lab demo. But first, let’s take a look at what’s in the box.

Unboxing and Packaging

The Halcyon ships in a more premium presentation than the budget Kiwi Ears models. The front shows the chrome IEMs and bills it as a “1DD + 1 MEMS + 3 BA Tribrid”, with the side panels covering the specifications and the driver technology:

Lifting off the outer sleeve reveals a black Kiwi Ears inner box, with the IEMs presented in foam beneath:

A zip-up hard carrying case is included, holding the cable and the tips:

The box is well stocked:

• The Halcyon IEMs
• An interchangeable-plug cable
• 3.5mm SE and 4.4mm BAL adapters
• Two styles of silicone ear tips (wide-bore and narrow-bore, three sizes each)
• Six replacement filters
• The hard case and documentation

Here’s everything laid out:

Two styles of silicone tips are included — wide-bore and narrow-bore, in three sizes each — which give you a first layer of tuning before you even touch the filters:

Design and Build Quality

The Halcyon’s shells are CNC-machined aerospace-grade aluminium with a chrome-like finish, and at 5.99g each they are light for a metal-bodied tribrid:

The shape is ergonomic, with a 6.2mm nozzle topped by a mesh grille:

The inner side carries the “Kiwi ears Halcyon” engraving and a flush 0.78mm 2-pin socket, and the nozzle mesh is neatly finished:

The six replacement filters let you keep the nozzle mesh clean over time:

A closer look at a single shell on its own shows off that chrome-like machined finish and the mesh grille more clearly than the paired shots above:

Set beside another IEM from the collection, the Halcyon’s shells are the rounder shape of the two, and compact with it — I think this is the smallest shell on any of the premium Kiwi Ears IEMs. Together with the 5.99g weight that makes it the most comfortable IEM I have worn for long sessions. The one thing to be aware of is that the rounded shape is slightly unusual, so not everyone will land a perfect seal first time — and on this IEM the seal is what the sub-bass depends on, so it is worth working through the eartip sizes rather than settling:

Isolation is good too — enough to be useful on a commute without going out of its way to be a noise-blocker.

Seen from the inner side, the differences in shell profile and nozzle between these and the other IEMs I reach for most are clearer than any measurement of them:

Nozzle length and angle vary more between IEMs than people tend to assume, and that is worth keeping in mind whenever you see two of them overlaid on the same graph.

Cable and Connectivity

The supplied cable is a 4-core braided 4N single-crystal silver-plated copper, with a modular plug system — the connector unscrews so you can swap between the included 3.5mm single-ended and 4.4mm balanced adapters:

At the IEM end it uses standard 0.78mm 2-pin connectors with clear L/R polarity markers, and there is a chin slider on the cable:

Because the Halcyon uses a standard 2-pin system, it is also compatible with other cables — including Kiwi Ears’ optional USB-C cable with embedded DSP equalisation, which works with the Halcyon app to let you tune the sound to your own preference, and an optional gaming boom-mic cable for calls and games. That makes it as flexible for gamers as it is for audiophiles, in the same vein as the S-Link cable. Both of those cables are sold separately — what is in the box is the modular 3.5mm/4.4mm cable and nothing else.

MEMS Driver Technology

MEMS stands for Micro-Electro-Mechanical Systems, and it is worth explaining because it is the reason this IEM exists in the form it does.

A conventional driver — dynamic or balanced armature — moves air with a physical assembly: a coil, a magnet, a diaphragm suspended on a surround. A MEMS driver is a solid-state device instead. It is fabricated on a silicon chip using semiconductor processes, and the moving element is etched into the silicon itself rather than assembled from separate parts. Because it is a chip, it needs supporting passive components to drive it, and those sit inside the shell alongside it.

The practical argument for MEMS is where it sits against electrostatic drivers. EST tweeters are the usual way to get very fast, very extended treble, and they are expensive — they need high voltages, dedicated transformers, and they push an IEM well up the price ladder. MEMS is being offered as a cheaper route to a similar goal: a transducer with very low moving mass and no coil, aimed at the same top-octave speed and extension, but manufactured like a chip rather than hand-assembled.

Kiwi Ears’ claims for it are ultrasonic operating speed and near-zero phase distortion. Those are the manufacturer’s figures rather than anything I have verified — a coupler measurement cannot confirm either of them — so treat them as the design intent rather than as a result. What I can say is that MEMS drivers remain rare in shipping products, and the Halcyon is the first one I have had in a finished IEM rather than a demonstration.

One thing worth being clear about: MEMS microphones have been commonplace for years, in phones, laptops and the inline mics on plenty of budget earphones. A MEMS driver — the same technology used to produce sound rather than capture it — is the new part, and the two should not be confused.

Sound Impressions

I listened over the balanced cable from a desktop source, and also from a dongle to see whether it needed more than that. It does not. The Halcyon asks for a little more juice than a typical IEM, but nothing dramatic — at 29Ω it is not hard to drive, and a decent dongle is enough. You will just find yourself a few steps further up the volume control than usual.

The Halcyon follows Kiwi Ears’ studio-neutral house tuning, with the defining twist being the MEMS-driven top end.

Bass

There is proper sub-bass here, and it is the kind I like — it goes deep and it rumbles rather than thumping at you, and it stays where it belongs instead of smearing into everything above it. On “Limit to Your Love” by James Blake the low swells arrive as real physical weight while the rest of the track stays clean around them.

One thing matters more than usual on this IEM: get the fit right or you will not hear any of that. The Halcyon is sensitive to seal, and if you are even slightly off with the eartip size the bass is the first thing to go — it thins out and you end up wondering what the fuss is about. Work through the supplied sizes properly before you form a view on the low end. That is true of most IEMs, but it is more true of this one.

Midrange

The midrange is clean and well separated, and vocals stay clear and intelligible even with the bass doing as much as it does. Nothing is smeared and nothing is shouted at you. On “Fast Car” by Tracy Chapman the vocal sits where it should, with an even, honest presentation.

What you are hearing in the lower midrange is the Harman tuck rather than any thinness — it does not carry the extra warmth down there that has become common in the JM-1-inspired tunings a lot of makers have moved toward. Which you prefer is a matter of taste rather than one being correct; if you have been enjoying the warmer JM-1 house sound, this will read as the leaner of the two.

Treble

The treble is the part I keep coming back to, and it is where the Halcyon earns the MEMS driver. It is detailed and airy without ever being sharp — there is a real sense of space and extension up top, but it never tips into the hardness or splashiness that usually comes with chasing that kind of detail. On “Chocolate Chip Trip” by Tool the cymbal work has crispness and rapid decay while keeping its composure.

The shape of it is the part worth understanding. There is a recession in the lower treble — an approach that has become popular for good reason, because that is the region that turns fatiguing first — while the upper treble keeps real energy from the MEMS driver. You get the air and extension without the hardness that usually comes attached to it. If you want bite and sparkle pushed at you this is not that IEM, but if you are treble-sensitive it is exactly why you should look at it. The eartips give you room to move in either direction, as noted in the measurements section.

Soundstage and Imaging

This is a strong area. There is genuine separation and layering, the stage is larger than I expect from an IEM at this size, and placing instruments within it is easy. On “Hotel California” by the Eagles the instruments sit clearly apart from each other with precise placement. The overall character is composed and unforced rather than explosive — it presents detail rather than throwing it at you.

Specifications and Measurements

Specifications

The figures above are Kiwi Ears’ own published specification. My own measurements follow below.

All the measurements below were taken on my own clone IEC60318-4 coupler. You can open them interactively, and overlay the Halcyon against anything else in the database, on the Pragmatic Audio measurement page.

Frequency Response

Here is the Halcyon against the Harman Adjusted and JM-1 targets, both channels shown:

The bass tracks Harman closely, with that typical Harman “tuck” where the shelf returns to the target before it reaches the midrange. Channel matching is excellent — the two traces sit on top of each other. It is a very similar picture to my favourite recent Kiwi Ears, the Astral.

What I like more here is what the Halcyon does with the treble. The lower treble is pulled back where the Astral keeps more energy, and there is a narrow band of air higher up where the MEMS driver is working — and that combination gives the Halcyon a character of its own rather than just being a restatement of the house tuning.

Comparisons

The Kiwi Ears Astral is the obvious comparison, since it is the closest thing in the same house tuning:

Below about 4kHz these are near enough the same IEM — the bass shelves overlap and the midrange runs within a decibel of each other, so the two have far more in common than their different driver technologies suggest. All the meaningful difference is in the treble, and it is the part I prefer on the Halcyon: the lower treble is pulled back where the Astral holds more energy, and the MEMS driver adds air higher up that the Astral’s armature tweeter does not reach in the same way. Build is the other contrast — the Astral’s transparent resin against the Halcyon’s CNC aluminium — and neither feels like the compromise.

Against the Juzear Nimbus:

The two are identical in the deep bass, but the Nimbus carries more through the lower midrange, which gives male vocals and cellos more body. Their treble peaks land in different places.

Here they are together — the Daybreak on the left, the Halcyon top right and the Astral below it:

The size difference matters on its own: the Daybreak is a considerably larger shell than either Kiwi Ears, which is part of why it fits differently and, as noted above, why comparing measurements across shells of different geometry needs a little caution.

And against the CrinEar Daybreak:

The Halcyon is the bassier of the two by a clear margin, and carries a little more presence-region energy through 1–2.5kHz. The pinna gain is almost identical.

Two I have not measured

The current Kiwi Ears line-up, faceplates up:

I have not run the other two Kiwi Ears models people usually ask about alongside this one, so what follows is on driver configuration and price rather than on graphs.

The Septet at $269 is the quadbrid — a dynamic driver, four balanced armatures, a micro-planar and a piezoelectric driver. It covers the spectrum by giving each region its own dedicated technology; the Halcyon uses fewer driver types but pushes the very top end further than a conventional armature goes. Broader complexity against a more singular treble story.

The Orchestra II at $299 is all balanced armature, and is prized for its midrange. It shares the Halcyon’s neutral leanings but arrives there without a dynamic driver, so the Halcyon has the more physical low end while the Orchestra II has the more unified, single-driver-like midrange that an all-BA design can give you.

Eartips

The Halcyon ships with two tip styles — wide-bore and narrow-bore, three sizes each — and swapping between them changes the treble subtly. That is worth knowing, because it means you have a way to adjust the top end without reaching for EQ at all. If you want a little more or less treble than the stock setup gives you, try the other tips before you touch a filter.

One minor observation while I am here. The selection is good, but having recently reviewed a few sub-$100 IEMs that ship with more generous tip sets, I was mildly surprised by what Kiwi Ears include at this price. It makes no difference to me personally — I use third-party tips on almost everything — but if you rely on the supplied set, it is worth knowing there is a little less choice here than the price might lead you to expect.

Distortion

Distortion was measured at a deliberately high level — the fundamental sits between roughly 95dB and 105dB SPL across the sweep, which is louder than I would actually listen:

Read as a percentage, second-harmonic distortion sits around 1.5–1.8% in the lowest bass, falls to about 1% by 60–100Hz, and settles near 0.5% from 200Hz through 2kHz, with a rise to roughly 1.2% around 3kHz. Third and higher harmonics stay below about 1% throughout, clustering in the 200Hz–2kHz band.

At 1kHz the figure is comfortably inside Kiwi Ears’ quoted <1% specification. The elevated deep-bass number is normal for a dynamic driver being asked to produce a 10dB shelf at over 100dB SPL, and at sane listening levels it will be well below what is shown here.

Rating Explanation

The Pragmatic Rating of 5 reflects a tribrid that backs up its ambitious technical premise with a coherent result rather than a driver count for its own sake. The MEMS-led treble resolved fine detail for me — cymbal texture and decay stayed separable — and I did not hear hardness on my sample, though the measured 7.5kHz peak will still be a limitation for some listeners; the 10mm dynamic gives a clean, weighty sub-bass shelf without muddying the mids, and the DEK armatures keep the midrange natural — the studio-neutral tuning with its measured sub-bass boost is well judged. The aerospace-aluminium build is light and solid, the accessory set is generous, and the standard 2-pin system means it can become a gaming headset or a tunable EQ platform if you buy the optional USB-C DSP or boom-mic cable, and a straightforward balanced IEM if you do not.

At $259 it sits in a competitive mid-fi bracket, which is the main thing to weigh — this is no longer the $199 Kickstarter bargain. The measurement rating reflects what the graphs actually show: a bass shelf that extends fully to 20Hz and returns to target by 200Hz, and pinna gain that lands on Harman at 3kHz. It is held to four rather than five by the 4–6kHz recession and the narrow 7.5kHz peak, which are deliberate voicing choices rather than faults, but are the two places the response departs most from the target.

This one is for the listener who wants a technically advanced, studio-neutral tribrid with standout treble resolution, and who values the flexibility to run it balanced, over USB-C with DSP EQ, or with a gaming mic.

Conclusion

The Kiwi Ears Halcyon is the most interesting of the three Kiwi Ears products I have been using and the one that best justifies its place. Building a tribrid around a solid-state MEMS driver is a genuinely novel move, and it pays off in a fast, detailed, well-extended top end, supported by a clean sub-bass shelf and a natural midrange that follow Kiwi Ears’ studio-neutral house sound.

It is no longer the Kickstarter steal it was at $199, but at $259 the MEMS treble and the cable ecosystem it shares with the S-Link still make it worth the asking price on their own. Of the three Kiwi Ears products I have been using, this is the one I keep reaching for, and it wins on two things specifically: it is the most comfortable of them by a clear margin, and the MEMS-led top end gives it a character the other two do not have.